1. Field of the Invention
The invention relates to a shifter for actuating at least one gear mechanism of a bicycle.
2. Description of the Related Art
German Patent Application P 3 501 951.4 describes a shifting device for a multi-stage gear mechanism of a bicycle in which a shift lever is mounted with freedom to pivot on a journal pin attached to a housing. A central section of the shift lever is designed as a winding drum for the shift-control cable. The central section of the shift lever is also provided with latching stages for engagement with a latching pawl mounted on the base part of the shifter so that it can swing in the radial direction. The latching pawl is under the influence of the restoring force of the tensioned shift-control cable and is additionally provided with its own spring element which urges the latching pawl to swing outward. The advantages of a shifting device designed in this way are that it requires only a few parts which are easy and simple to manufacture and that it offers good functionality at low production cost. A problem with this shifting device is that there are certain limitations on its functionality, because delays can occur in the shifting operation when a problem in the gear hub, for example, prevents the gears from shifting easily from one stage to another. When that occurs, the influence of the restoring force of the tensioned shift-control cable disappears for a short time and the shift lever is unable to exert any effect for that short time.
British Patent No. GB 2,012,893 A discloses a shifter for bicycle gears designed as a step-type or trigger shifter which establishes the individual gear positions using pawls which may be used both to shift and also to hold the selected gear. This is a two-lever shifter, in which a first shift lever exerts tension on a control cable in the tensioning direction and a first pawl rotates a winding drum on which the control cable is wound by engaging with a set of latching teeth. The control cable is released to move in the release direction by a second lever which lifts a second pawl out of a second set of latching teeth and releases the control cable in a series of steps according to the principle of a balance wheel in a mechanical watch. Two pawls and two shifters are required to execute these relatively simple shifting operations in the two directions. This shifter is complicated and it still does not have a design which can be considered optimal in terms of ergonomic usability.
The proposed shifter according to the present invention consists essentially of only three parts which are easy to manufacture by the injection-molding process. In this shifter, a transfer means is attached to a movable element, which can either tension or release the transfer means. This movable element is supported together with a gripping element in a housing with the freedom to pivot around a center of rotation in the housing. A pawl on the movable element engages with a set of latching teeth in the housing and in this way defines the individual gear positions of the gear mechanism of the bicycle. A spring is also connected to the gripping element. The spring works together with the gripping element such that the transition from one latching stage to another acquires an initial acceleration in the release direction of the transfer means. This speeds up the shifting operation in the release direction and increases the preload on the transfer means normally provided by the gear mechanism. This is because the pawl of the movable element is not raised by the lifter on the gripping element until the spring has been able to exert a certain amount of preload on the movable element. As a result of this preload, the mechanism is then able to arrive at the next gear position at an accelerated rate.
The object of the present invention is therefore to create a shifter which consists of only a few, easily made parts, which is easy to shift both in the tensioning direction and in the release direction, and which makes it possible for the tensioning means to change from a first to a second gear position of the gear mechanism at an accelerated rate in particular in the release direction.
The object is met by a shifter for actuating at least one gear mechanism of a bicycle including a housing having a set of latching teeth, a gripping element arranged on the housing and selectively moveable relative to the housing in a release direction and a tensioning direction for actuating the shifter, and a movable element movably arranged on the housing and connectable to a gear transfer means for tensioning and releasing the gear transfer means. The movable element includes a pawl operatively arranged for engaging the set of latching teeth arranged on the housing. A lifter is arranged on the gripping element operatively arranged for disengaging the pawl from the set of latching teeth when the gripping element is moved in the release direction. A spring is arranged on the movable element and a driver is mounted on the gripping element. The driver is operatively arranged for preloading the spring when the gripping element is moved in the release direction for urging the movable element toward the release direction.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.